Practical Engineering: Holding the Roof Up

The morning following a recent heavy
snowstorm, I got an emergency call
about a roof collapse. It was, in fact, an
example of what we engineers call "catastrophic
failure" — a classic case of
underdesigned (or undesigned?) eaves
tie connections. Although these things
don't occur often, such a collapse serves
as a reminder of wha t migh thappen if
connections are not properly designed
and executed in the field.
This old, solidly built structural-brick
building had full-size 3x8 attic floor
joists at 16 inches on-center, with full
1-inch-thick plank flooring. (As it
turned out, the sturdy attic floor saved
the day, halting the fall of the roof
assembly and preventing damage to the
walls and ceilings below.) The